Thirty-two tight gas wells completed in the Cleveland Formation in Lipscomb County, Texas were analyzed to determine the effectiveness of using production rates to evaluate completion techniques. Production rate tools tested were rate-versus-time, cumulative-versus-time and rate-versus-cumulative graphs of the first six months, twelve months and twenty-four months of production. The standard used to measure the validity of conclusions from the production curves was the frac length of each well as determined by inverted decline curve analysis. Comparisons between offset wells and also between groups of wells (using frac lengths to group the wells into quartiles) resulted in the wrong conclusion about half of the time. In other words, flipping a coin to determine the best frac treatment would have been just as effective as comparing production rates. The most likely reasons for this failure of production rate evaluation techniques are lack of uniformity of reservoir characteristics and boundaries to the drainage area.

The conclusion is that, at least for the wells studied, some analytical method of determining treatment effectiveness such as Fetkovich curves, inverted decline curve analysis or buildup analysis should be used to evaluate various types and sizes of frac treatments. Production comparisons can be misleading if they are not validated by analytical methods.

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